Electrical over/under voltage automatic disconnect apparatus and method

Abstract

An analog or digital circuit that senses both low and high input voltage and operates to disconnect both line and neutral electrical power connections to a protected device when abnormally low or high voltages are received from a single- or multi-phase power source, and reconnects the protected device when input power has stabilized. The sensing circuit and power supply is functional with voltages up to at least 240 Vac. The nominal 120 Vac circuit is designed to withstand a 6 kilovolt surge without damage. The apparatus does not disconnect the ground line during an out-of-tolerance voltage condition.

1. An electrical apparatus comprising:
 connecting means for connecting the apparatus to a supply of at least one phase of alternating current power having a line, neutral and ground; 
 sensing means for sensing the voltage of the supplied power across the line-neutral, line-ground and neutral-ground; 
 distribution means having corresponding line, neutral and ground for distributing the sensed power; and 
 disconnecting means for disconnecting the line and neutral from the sensed power when the sensing means detects an out-of-tolerance voltage condition, 
 whereby the sensing means deactivates the disconnecting means when the sensing means no longer detects an out-of-tolerance voltage condition. 
 
   
   
     2. The apparatus in accordance with  claim 1  wherein the connecting means is a three-conductor electrical cord having a three-prong plug and the distribution means is at least one three-prong receptacle. 
   
   
     3. The apparatus in accordance with  claim 1  wherein the sensing means is selected from a group comprising analog circuitry and digital circuitry. 
   
   
     4. The apparatus in accordance with  claim 1  wherein the supply of alternating current power is a three phase source. 
   
   
     5. The apparatus in accordance with  claim 1  wherein the connecting means is a relay having separate contacts for the line and neutral. 
   
   
     6. The apparatus of  claim 3  having a reconnecting means for reconnecting the sensed power to the distribution means when the sensing means no longer detects an out-of-tolerance voltage condition. 
   
   
     7. The apparatus of  claim 6  wherein the reconnecting means has a delay of approximately 15 seconds when the sensing means no longer detects an out-of-tolerance voltage condition. 
   
   
     8. An electrical apparatus comprising:
 connecting means for connecting the apparatus to a supply of at least one phase of alternating current power having a line, neutral and ground; 
 sensing means for sensing the voltage of the supplied power across the line-neutral, line-ground and neutral-ground, wherein the sensing means can detect voltages in excess of 132 Vrms and voltages of less than 60 Vrms; 
 power surge absorption means; 
 distribution means having corresponding line, neutral and ground for distributing the sensed power; 
 disconnecting means for disconnecting the line and neutral from the power source when the sensing means detects an out-of-tolerance voltage condition, wherein the sensing means activates the disconnecting means before the apparatus suffers electrical damage; and 
 said sensing means deactivates said disconnecting means when the sensing means no longer detects an out-of-tolerance voltage condition. 
 
   
   
     9. The apparatus of  claim 8  wherein the sensing means is selected from a group comprising analog devices and digital devices. 
   
   
     10. The apparatus in accordance with  claim 8  wherein the out-of-tolerance voltage condition is a voltage of less than approximately 60 Vrms or greater than approximately 132 Vrms. 
   
   
     11. The apparatus of  claim 8  wherein the deactivation of said disconnecting means has a delay of approximately 15 seconds when the sensing means no longer detects an out-of-tolerance voltage condition. 
   
   
     12. The apparatus of  claim 8  wherein the deactivation of said disconnecting means has a delay of approximately 15 seconds when the sensing means no longer detects an out-of-tolerance voltage condition.